Experimental kerma coefficients and dose distributions of C, N, O, Mg, Al, Si, Fe, Zr, A-150 plastic, Al₂O₃, AlN, SiO₂and ZrO₂for neutron energies up to 66 MeV

Abstract

Low-pressure proportional counters (LPPCs) with walls made from the elements C, Mg, Al, Si, Fe and Zr and from the chemical compounds A-150 plastic, AlN, Al2O3, SiO2 and ZrO2 were used to measure neutron fluence-to-kerma conversion coefficients at energies up to 66 MeV. The LPPCs served to measure the absorbed dose deposited in the gas of a cavity surrounded by the counter walls that could be converted to the absorbed dose to the wall on the basis of the Bragg-Gray cavity theory. Numerically the absorbed doses to the walls were almost equal to the corresponding kerma values of the wall materials. The neutron fluence was determined by various experimental methods based on the reference cross sections of the 1H(n, p) scattering and/or the 238U(n, f) reactions. The measurements were performed in monoenergetic neutron fields of energies of 5 MeV, 8 MeV, 15 MeV and 17 MeV and in polyenergetic neutron beams with prominent peaks of energies of 34 MeV, 44 MeV and 66 MeV. For the measurements in the polyenergetic neutron beams, significant corrections for the contributions of the non peak energy neutrons were applied. The fluence-to kerma conversion coefficients of N and O were determined using the difference technique applied with matched pairs of LPPCs made from a chemical compound and a pure element. This paper reports experimental fluence-to-kerma conversion coefficient values of eight elements and four compounds measured for seven neutron energies, and presents a comparison with data from previous measurements and theoretical predictions. The distributions of the absorbed dose as a function of the lineal energy were measured for monoenergetic neutrons or, for polyenergetic neutron fields, deduced by applying iterative unfolding procedures in order to subtract the contributions from non-peak energy neutrons. The dose distributions provide insight into the neutron interaction processes.

Theoretical calculation of kerma coefficients for n+ 16 O reaction below 30 MeV

“…3. The experimental data (full square) [17] [18] are derived from different oxides, and the residual data (full dot) [13] are measured by Meulders et al Using the elastic cross sections and the 1st Legendre coefficients of ENDF/B-VIIb.3, we can reproduce the structural curves of the elastic recoil kerma coefficients below 30 MeV and the total kerma coefficients in the lower energy region. However, the present work underestimates the total kerma coefficients at about 6-20 MeV neutron region, and overestimates them above 20 MeV.…”

New calculation method of neutron kerma coefficients for carbon and oxygen below 30 MeV

“…[35], and the other experimental data (open squares, full dots) are derived from Refs. [2,4], respectively. The evaluated results of Ref.…”

“…The three Schrewe experimental data sets (see legend) are derived from different oxides in Ref. [2], and the residual data (full dots) are from Ref. [4].…”

“…This direct measurement of kerma coefficients is difficult, and the measured values are available only for a few elements and neutron energies. Moreover, such measurements require total particle equilibrium in the studied volume and necessitate significant corrections [2]. The second method uses experimental cross * sxj0212@mailbox.gxnu.edu.cn sections, which requires information on all significant reaction channels, including angular and/or energy distribution and energy-angle distribution of secondary particle.…”

New calculations of neutron kerma coefficients and dose equivalent

“…Neutron kerma coefficients, absorbed dose and dose equivalent data are important in radiation protection and therapy. For neutron kerma coefficients, several calculations (Caswell et al 1980, Alekseev et al 1986, Slypen et al 2000 and numerous measurements (DeLuca et al 1984, Menzel et al 1984, Wuu and Milavickas 1987, McDonald and Cummings 1988, Hartmann et al 1992, Benck et al 1998, Schrewe et al 2000, Bergenwall et al 2004 have been reported. A problem is that, due to the lack of precise experimental cross section data and different treatments for high-energy neutron interaction with light nuclei and compounds, marked discrepancies have appeared between various results for kerma coefficients.…”